Precat removal - How I did it...

[Anonymous]

Thanks I was actually installing Che's header. I just eyed the torqueing. I didnt get the specs in time, but seems like the install went well. I hear a minor air leak at the manifold head gasket. Should be an easy fix(need to torque it more). Went for a little test drive and it sounds great. My idle used to be rough at 600 and now it idles around 800. I blame the pre-cats for that.

[Anonymous]

Took me all day today but i am now pre-cat free!!    s:D s:D  

Also fitted a TEE twin exit exhaust at the same time   s8) s8)  

Definately seems to pick up quicker imo.

I am told that TTE exhausts does not increase power so unlikely to be that?   s:?: :?: s:?:  

Hardest bit was remembering where everything went!!   s:shock: :shock: s:shock:

[Anonymous]

i will be doing after nct/mot in sept,what did you do to clean it up ,air hose or power wash ?
cheers
jay

[markiii]

use water to be sure

[Anonymous]

i will be doing after nct/mot in sept,what did you do to clean it up ,air hose or power wash ?
cheers
jay

Morning Jay,

Mark is right.

to be honest there was very little in the way of dirt or rubbish in the manifold to be honest. However, i used a narrow wheel cleaning brush and and hose pipe, (Under Pressure) to just scrub it out to be sure. Then blasted water down all the holes i could see and then dried it in the sun. Then had a good luck inside all the holes with a torch.

Hope that helps   s:) s:)  

Jamie

[Anonymous]

Today I decided to check the pre-cats, it was the first opportunity I had since my g/f got her car. Managed to get it onto a lift at my pop's garage and get the manifold off, I was quite pleased to see that the precats were in 100% perfect condition with no cracks or anything broken off. I soon fixed that with a large Barry Scott screwdriver  ........... Bang, and the precats are gone  s:P s:P

However, when I put everything back together and started the car it sounded ok and seemed to be normal for the first 5 mins ...... shortly after though, there seemed to be a bit of smoke rising from the engine. I'm hoping it's just unburnt oil or possibly WD40 (which I sprayed liberally around all bolts) burning up, but it didn't smell like that   s:? :? s:?   ........... I can't think of any other reason for smoke to appear after a manifold off/manifold on job which didn't involve any work in the actual engine. All bolts are tightened, o2 sensors back in proper place, etc. Anyone else ever had this after gutting the pre-cats?

[Barney Bear]

Hi to all

having read all the posts relating to this pre cat issue could you please advise me

would all of you recomend this removal

I have a 04 so cant work out if its no longer a problem due to early failures, hoping that Toyota came up with a better pre cat for later models to stop this problem

only had my 2 for one week now and given I wont even park it next to another car so I dont get those nice dents given by twits that fling thier doors open without any care, I really dont want something like PC failure to happen

I do have a warranty from the Mr T dearlership but dont know wether to have it done now or when the warranty ends

as my experiance tells me warranties are just a piece of paper and no more

would value your comments

Teddy BB
I

[Barney Bear]

Hi to all

having read all the posts relating to this pre cat issue could you please advise me

would all of you recomend this removal

I have a 04 so cant work out if its no longer a problem due to early failures, hoping that Toyota came up with a better pre cat for later models to stop this problem

only had my 2 for one week now and given I wont even park it next to another car so I dont get those nice dents given by twits that fling thier doors open without any care, I really dont want something like PC failure to happen

I do have a warranty from the Mr T dearlership but dont know wether to have it done now or when the warranty ends

as my experiance tells me warranties are just a piece of paper and no more

would value your comments

Teddy BB
I

[andywood]

I've got an 03 in mint condition and went through the same decision process when i got mine at the start of this year. It only had 10k on the clock and pre-cat failure was in my mind low risk due to the tweeks done by Toyota as part of the facelift upgrades, but for me it purely came down to not wanting to risk leaving them in.
Took them out myself without any major issues, got a slightly better exhaust note and a more freely flowing engine. Now wondering why I would have ever wanted to leave them in!
You have no doubt read all the info about them serving no purpose for the UK emissions leglislation and MOT, many people on here have also passed MOT's with no probs with them out.

Endless chicken/egg debates about if pre-cat failure causes cylinder oil seal issues or vice-versa. Again though, some may argue if the car is ok then don't try to fix what ain't broke, but for me it was just a matter of removing the potential risk.

Chance of failure is probably tiny and if you left them in you would probably be fine for the rest of the cars life.
Forums do attract people with problems and sometimes therefore paint a slightly biased picture.
The car in general is very reliable and well built, so an issue like this even with relatively low failure rates is always going to get thrown into the lime-light.

The decision is yours   s:wink: :wink: s:wink:  

Andy.

[andywood]

forgot to mention, if you do decide to take them out, be very very careful not to cross-thread the mounting threads on the oxygen-sensors   s:oops: :oops: s:oops:

[Barney Bear]

Thanks Andy

think you have just settled the debate

will have it done as soon as possible , as like you, would rather prevent  than cure

will have a word with my garage as dont think it is something i can do

thanks for your advise
  s:D s:D

[andywood]

No worries Bear

In case you didn't realise, there is a section on here for companies who do the removal:

 m http://www.mr2roc.org/phpBB2/viewtopic.php?t=11137 m

[Anonymous]

Hi all!
My name is Arthur, I'm from Latvia  s:) s:)  
I'm really sorry about my english grammar etc. but I just want to get simple answers to simple questions  s:!: :!: s:!:  
If I'm not wrong, there are 2 cats - precat and main cat! If I remove precat what will change, torque and rev will be better? If I remove main cat, what would go wrong... what happens with Lamda sensors and ECU?
In Latvia aren't strong emission laws etc. so I can make straight exhaust! But only I must be under 90db with the exhaust noise on 3Krp/m

In Latvia are aprox. 5-10 ZZW30 MR2's no one is making mods etc. so I am first in my country who wants to do something more with that car  s:lol: :lol: s:lol:   s:) s:)


Thanks

 Arthur

[Anonymous]

Had a nightmare!

2001 1ZZ, had to cut / grind off the upper and lower heatshield bolts with a Dremel, after 3 days of soaking with Plusgas. Every nut lossened bar one on the manifold (top left), which has now stripped completely. Currently trying to grind off enough of the nut to remove it without mutilating the stud too much....

Anyone have any good ideas on how to remove it? The stud is solid as well.....

  s:( s:(

[roger]

Hi all!
My name is Arthur, I'm from Latvia  s:) s:)  
I'm really sorry about my english grammar etc. but I just want to get simple answers to simple questions  s:!: :!: s:!:  
If I'm not wrong, there are 2 cats - precat and main cat! If I remove precat what will change, torque and rev will be better? If I remove main cat, what would go wrong... what happens with Lamda sensors and ECU?
In Latvia aren't strong emission laws etc. so I can make straight exhaust! But only I must be under 90db with the exhaust noise on 3Krp/m

In Latvia are aprox. 5-10 ZZW30 MR2's no one is making mods etc. so I am first in my country who wants to do something more with that car  s:lol: :lol: s:lol:   s:) s:)
Thanks
 Arthur

Hi Arthur, and welcome...looks like you have been forgotten!

Removing the precats (there are 2 of them) increases noise, and there might be a small change in performance, but nothing significant. Emissions (for UK testing purposes) aren't affected.

Removing the main cat (by putting in a de-cat pipe) will increase noise even further, to what level not sure. Fairly certain it will be above 90Db. Emissions will go up, of course. The new pipe should have a hole for the Lamba (O2), though it will be necessary to sort it since it reads emissions. This might give you an insight.

[kanujunkie]

just to clarify for you Arthur, there are 3 cats. The system is in fact called Three Way Cat (TWC) which consists as Roger has said of 2 pre-cats and 1 main cat

as for the noise levels, your going to be pushing 100dB+ if you remove everything, Aarons 2 sound more like a spitfire at the moment and he still has minimal exhausts system, its deafening. As for the 3rd o2 sensor, that can be got rid of with a signal conditioner and resistor package but you need to keep the main ones although they can be reduced down to 1 with some spliceing and a resistor

[Anonymous]

Hello again  s:) s:)
now I get my car from Germany after 2 month waiting  s:) s:)  

I already removed precat, there was only one  s:? :? s:?  and the engine soon be dead - dramaticaly burns oil! So I need to change piston rings! And the question is, which aftermarket rings will be better? TOY OEM rings is too expensive for me - 140pounds!  s:roll: :roll: s:roll:  Local Toyota dealer sent me price list of full replacement parts aprox 450pounds (gaskets, rings, cranckshaft bearings) but it's damn to expensive... in eBay these things I can get much more cheaper  s:arrow: :arrow: s:arrow:   m http://cgi.ebay.com/ebaymotors/ws/eBayI ... gory=33623 m

but how good they are?
Maybe someone can post some link to same problem?

an there is my MR2  s:arrow: :arrow: s:arrow:   m http://www.burnout.lv/index.php?pg=40&album=35 m


P.S. I'm sorry about offtoic in this thread, please admin move this post to right topic  s:) s:)

thanks!

[enid_b]

thats bad news arthur, i am sorry to hear that.

i hope you can fix the problem soon and for not much money

E

[Anonymous]

thats bad news arthur, i am sorry to hear that.

i hope you can fix the problem soon and for not much money

E

Thanks enid_b  s;) s;)  but I need a solution for these piston rings  s:idea: :idea: s:idea:  only then I can fix my engine  s:) s:)

[tselwyn]

Just to post a positive reply on the topic of pre-cats:

My pre-cats were removed a couple of months ago - and my car was MOT'd last week at the local (ridiculously expensive last time I go there) Mr T.

Despite the poor service, the upside is that it passed MOT.   s:P s:P  

Don't think there's a list on the forum of how many cars have pre-cats  out, and are passing MOTs - but mine did!  So get them out!

Tim.

[Liz]

Sorry to burst your bubble - but a car having pre-cats out has never been an issue for MOT seen as they are not a requirement for emissions in this country - the ones who worry are those with down pipes and no main cat.  s:wink: :wink: s:wink:

[tselwyn]

I realise that Liz (only needed for California, etc)!  

But as andy and "Teddy BB" have mentioned in this thread, you are always sitting there on the fence (before you do it) - wondering if you're going to mess your emissions up by taking them out - despite the fact everyone on here tells you to take them out cos of the potential consequences.

It's more a "but Toyota have put them in, so should I really take them out cos MR2ROC says so" worry - that I had before I plucked up courage and got them removed.

The issue is that everyone always says that there are no issues, but no one had posted in this thread that they have had them out, and that they've passed their most recent MOT.    s:wink: :wink: s:wink:

[edward.carter]

The issue is that everyone always says that there are no issues, but no one had posted in this thread that they have had them out, and that they've passed their most recent MOT.    s:wink: :wink: s:wink:

I have my precats out and i have passed my most recent mot.... 48 hours ago in fact. although they been out for 2-3 years and i have passed 2-3 mots since they have been out. no problems!!

[Anonymous]

Well thinking of getting a MR2 hence my first post.

Scary stuff and would be looking at a pre 2002 model to keep within budget. Will keep my ears to the ground for strange noises on test drive.

Just something that I thought might be useful but what sort of torque you supposed to do the bolts back up to??? Would be checking the pre cats as soon as I got one in order to make sure it was alright.

[spit]

Hello and welcome to the ROC  s8) s8)  

Just something that I thought might be useful but what sort of torque you supposed to do the bolts back up to???

I'm sure its detailed somewhere but I can't find it  s:oops: :oops: s:oops:  

Anyway, 5x block-manifold nuts are 27 ftlbs (which really isn't that much). And the mani-cat are 64 ftlbs I think.... but they'll be considerably tighter to get off!

Providing you go with new and genuine gaskets for reassembly you should be fine.

O2 sensors are officially 32 ftlbs, but a tight nip is plenty.
Heatshield bolts are academic, particularly if the old ones shear off! - without precats there's no real need to run with the heatshield.